Clinical Protocol support contract designed to attain extramural support for developing, designing, interpreting, and evaluating clinical trials, epidemiologic and natural history studies. In addition, it will provide for outcomes research involving eye diseases and visual disorders and some preclinical studies. The focus shall be on the design of studies and the collection, analysis, and interpretation of data emanating from these studies, as well as support, and monitoring patient safety and follow-up. Contractor shall also provide analytical and data management support, as described in the work statement, for specified clinical research data bases, cost-effectiveness and economic analyses, quality of life assessment and outcomes research. This will include, but not be limited to, the following areas: analysis of Medicare and other health care databases;evaluation of existing NEI databases such as, centralized NEI Intramural Research database, the Eye Disease Case Control Study, Early Treatment Diabetic Retinopathy Study, Framingham Eye Study, and intramural AIDS and uveitis databases. Objective of Clinical Protocol: This study will determine whether certain factors in the blood are associated with the severity of diabetic retinopathy.